p(x) = 6 - .0005x

The Revenue R(x) = xp(x) = 6x - .0005*x^2

Thr Profit is P(x) = R(x) - C(x) = 6x - .0005*x^2 - 3000 - 1.2x

P(x) = 4.8x -.0005x^2 -3000

Both the max profit and max revenue can be found by setting the respective derivatives equal to 0.